Periodic cleaning and sanitizing in the food process industry is a regimen mandated by law and rigorously practiced to maintain the exceptionally high standards of food hygiene and shelf-life expected by today's consumer. Residual food soil, left on food contact equipment surfaces for prolonged periods, can harbor and nourish growth of opportunistic pathogen and food spoilage microorganisms that can contaminate foodstuffs processed in close proximity to the residual soil. Insuring protection of the consumer, against potential health hazards associated with food borne pathogens and toxins and, maintaining the flavor, nutritional value and quality of the foodstuff, requires diligent cleaning and soil removal from any surfaces of which contact the food product directly or are associated with the processing environment.
The term "cleaning", in the context of the care and maintenance of food preparation surfaces and equipment, refers to the treatment given all food product contact surfaces following each period of operation to substantially remove food soil residues including any residue that can harbor or nourish any harmful microorganism. Freedom from such residues, however, does not indicate perfectly clean equipment. Large populations of microorganisms may exist on food process surfaces even after visually successful cleaning. The concept of cleanliness as applied in the food process plant is a continuum wherein absolute cleanliness is the ideal goal always strived for; but, in practice, the cleanliness achieved is of lesser degree.
The term "sanitizing" refers to an antimicrobicidal treatment applied to all surfaces after the cleaning is effected that reduces the microbial population to safe levels. The critical objective of a cleaning and sanitizing treatment program, in any food process industry, is the reduction of microorganism populations on targeted surfaces to safe levels as established by public health ordinances or proven acceptable by practice. This effect is termed a "sanitized surface" or "sanitization". A sanitized surface is, by Environmental Protection Agency (EPA) regulation, a consequence of both an initial cleaning treatment followed with a sanitizing treatment. A sanitizing treatment applied to a cleaned food contact surface must result in a reduction in population of at least 99.999% reduction (5 log order reduction) for a given microorganism. Sanitizing treatment is defined by "Germicidal and Detergent Sanitizing Action of Disinfectants", Official Methods of Analysis of the Association of Official Analytical Chemists, paragraph 960.09 and applicable sections, 15th Edition, 1990 (EPA Guideline 91-2). Sanitizing treatments applied to non-food contact surfaces in a food process facility must cause 99.9% reduction (3 log order reduction) for given microorganisms as defined by the "Non-Food Contact Sanitizer Method, Sanitizer Test" (for inanimate, non-food contact surfaces), created from EPA DIS/TSS-10, 07 Jan. 1982. Although it is beyond the scope of this invention to discuss the chemistry of sanitizing treatments, the microbiological efficacy of these treatments is significantly reduced if the surface is not clean prior to sanitizing. The presence of residual food soil can inhibit sanitizing treatments by acting as a physical barrier which shields microorganisms lying within the soil layer from the microbicide or by inactivating sanitizing treatments by direct chemical interaction which deactivates the killing mechanism of the microbicide. Thus, the more perishable the food, the more effective the cleaning treatment must be.
The technology of cleaning in the food process industry has traditionally been empirical. The need for cleaning treatments existed before a fundamental understanding of soil deposition and removal mechanism was developed. Because of food quality and public health pressures, the food processing industry has attained a high standard of practical cleanliness and sanitation. This has not been achieved without great expense, and there is considerable interest in more efficient and less costly technology. As knowledge about soils, the function of cleaning chemicals, and the effects of cleaning procedures increased and, as improvements in plant design and food processing equipment become evident, the cost effectiveness and capability of cleaning treatments, i.e. cleaning products and procedures, to remove final traces of residue have methodically improved. The consequence for the food process industry and for the public is progressively higher standards.
The search for ever more efficient and cost effective cleaning treatments, coupled with increasing demand for user friendly and environmentally compatible cleaning chemicals, has fostered a growing number of investigations which have significantly augmented understanding of soil deposition and removal processes by theoretical treatise rather than empirical experimentation. See, for example, "Theory and Practice of Hard-Surface Cleaning", Jennings, W. G., Advances in Food Research, Vol. 14, pp. 325-455 (1965); or, "Forces in Detergency", Harris, J. C., Soap and Chemical Specialties, Vol. 37 (5), Part I, pp. 68-71 and 125; Vol. 37 (6), Part II, pp. 50-52; Vol. 37 (7), Part III, pp. 53-55; Vol. 37 (8), Part IV, pp. 61-62, 104, 106; Part V, pp. 61-64; (1961) or "Physico-chemical aspects of hard-surface cleaning. 1. Soil removal mechanisms", Koopal, L. K., Neth. Milk Dairy J., 39, pp. 127-154 (1985). Such studies confirm that soil deposition on a surface and the sequential transitions of soil adherence to the surface (adsorption), soil removal from the surface and soil suspension in a cleaning/solution, can be described in terms of well established, generally accepted concepts of colloidal and surface chemistry. The significance of this association is that predictive tools now exist which assist the design of chemical cleaning compounds optimized for specific soils or formulated to overcome other deficiencies in the cleaning program.
These precepts suggest that a clean surface is difficult to maintain, that energy is released (entropy is increased) during soil deposition which favors physicochemical stability, i.e. a soiled surface is nature's preferred or more stable condition. To reverse this process and clean the surface, energy must necessarily be supplied. In normal practice, this energy takes the form of mechanical and thermal energies carried to the soiled surface. Chemical (detergent) additives to the cleaning solution (usually water) reduce the amount of energy required to reverse the energetically favored soiling process. Thus, the definition of detergent (Definition of the Word "Detergent", Bourne, M. C. and Jennings, W. G., The Journal of the American Oil Chemists' Society, 40, p. 212 (1963)) is "any substance that either alone or in a mixture reduces the work requirement of a cleaning process". Simply, detergents are used because they make cleaning easier. It follows that the word "detergency" is "then understood to mean cleaning or removal of soil from a substrate by a liquid medium." (Ibid.)
Soil removal cannot be considered a spontaneous process because soil removal kinetics require a finite period. The longer the cleaning solution is in contact with the deposited soil, the more soil is removed--to a practical limit. Final traces of soil become increasingly difficult to remove. In the last phase of the soil removal process, cleaning involves overcoming the very strong adhesive force between soil and substrate surface, rather than the weaker cohesive soil--soil forces; and, an equilibrium state is eventually attained when soil redeposition occurs at the same rate as soil removal. Thus the major operational parameters of a cleaning treatment in a food process facility are mechanical work level, solution temperature, detergent composition and concentration, and contact time. Of course other variables such as equipment surface characteristics; soil composition, concentration, and condition; and water composition effect the cleaning treatment. However, these factors cannot be controlled and consequently must be compensated for as required.
The food process industry has come to rely more on detergent efficiency to compensate for design or operational deficiencies in their cleaning programs. This is not to suggest that the industry has not addressed these factors; indeed, cleaning processes have changed considerably during recent years because of technological advances in food processing equipment and development of specialized cleaning equipment. Modern food processing industries have revolutionized their clean-up procedures through cleaning-in-place (CIP) and automation.
A major challenge of detergent development for the food process industry in the successful removal of soils that are resistant to conventional treatment and the elimination of chemicals that are not compatible with food processing. One such soil is protein, and one such chemical is chlorine or chlorine yielding compounds, which can be incorporated into detergent compounds or added separately to cleaning programs for protein removal.
Protein soil residues, often called protein films, occur in all food processing industries but the problem is greatest for the dairy industry, milk and milk products producers because these are among the most perishable of major foodstuffs and any soil residues have serious quality consequences. That protein soil residues are common in the fluid milk and milk by-products industry, including dairy farms, is no surprise because protein constitutes approximately 27% of natural milk solids, ("Milk Components and Their Characteristics", Harper, W. J., in Diary Technology and Engineering (editors Harper, W. J. and Hall, C. W.) p. 18-19, The AVI Publishing Company, Westport, 1976).
Proteins are biomolecules which occur in the cells, tissues and biological fluids of all living organisms, range in molecular weight from about 6000 (single protein chain) to several millions (protein chain complexes); and, can simplistically be described as polyamides composed of covalently linked alpha amino acids (i.e., the --NH.sub.2 group is attached to the carbon next to the --COOH group) of the general structure (L-configuration): ##STR1## where R represents a functional group specific for each alpha amino acid. Of over 100 naturally occurring amino acids, only 20 are utilized in protein biosynthesis--their number and sequential order characterizing each protein. The covalent bond that joins amino acids together in proteins is called a peptide bond and is formed by reaction between the alpha --NH.sub.3.sup.+ group of one amino acid and the alpha --COO.sup.- group of another (reactions occur in solution; and, alpha --NH.sub.2 groups and alpha --COOH groups are ionized at physiological pH with the protonated amino group bearing a positive charge and the deprotonated carboxyl group a negative charge) as illustrated for a dipeptide: ##STR2## wherein R.sub.1 and R.sub.2 represent characteristic amino acid groups. Molecules composed of many sequential peptide bonds are called polypeptides; and, one or more polypeptide chains are contained in molecular structures of proteins.
Polypeptides alone do not make a biologically functional protein. A unique conformation or three-dimensional structure also must exist, which is determined by interactions between a polypeptide and its aqueous environment, and driven by such fundamental forces as ionic or electrostatic interactions; hydrophobic interactions; hydrogen and covalent bonding; and change transfer interactions. The complex three-dimensional structure of the protein macromolecule is that conformation which maximizes stability and minimizes the necessary energy to maintain. In fact, four levels of structure influence a protein's structure; three being intramolecular and existing in single polypeptide chains, and the fourth being intermolecular associations within a multi-chained molecule. Principles of protein structure are available in modern biochemistry textbooks, for example: Biochemistry, Armstrong, F. B., 3rd edition, Oxford University Press, New York, 1989; or Physical Biochemistry, Freifelder, D., 2nd edition, W. H. Eruman Company, San Francisco, 1982; or Principles of Protein Structure, Schultz, G. E. and Schumer, R. H., Springer-Verlag, Berlin, 1979.
Protein interactions with surfaces have been studied for decades, with early focus on blood-plasma-serum applications and more recent emphasis in the so-called biocompatibility-biomaterials field or medical device implants. This work characterized the solid surface-protein solution interface and developed a range of new concepts and new experimental tools for research. Two comprehensive reviews of this literature are: "Principles of Protein Adsorption", in Surface and Interfacial Aspects of Biomedical Polymers, Andrade, J. D., (editor Andrade, J. D.), Vol. 2, pp. 1-80, Plenum Press, New York, 1985; and "Protein Adsorption and Materials Biocompatibility: A Tutorial Review and Suggested Hypotheses", Andrade, J. D. and Hlady, V., Advances in Polymer Science, Vol. 79, pp. 1-63, Springer-Verlag Berlin Heidelberg, 1986.
A growing source of protein adsorption information is now in literature, specifically dealing with soils. Studies have established that the same intrinsic interactions and associations within the protein molecule responsible for three-dimensional structure also attract and bind proteins to surfaces. Because of their size and complex structure, proteins contain heterogeneous modules consisting of electrically charged (both negative and positive) regions, hydrophobic regions, and hydrophilic polar regions, analogous in character to similar areas on food processing equipment surfaces having trace soil residues. The protein can thus interact with the hard surface in a variety of different ways, depending on the particular orientation exposed to the surface, the number of binding sites, and overall binding energies.
Because biological fluids such as milk are complex mixtures, the kinetics of the protein adsorption process are confused by concurrent events occurring at interfacial surfaces within the bulk solution and at the equipment surfaces. Temperature, pH, protein populations and concentrations, and presence of other inorganic and organic moieties have effect on rate dynamics. In general, however, there is general agreement that protein adsorption is rapid, reversible, and randomly arranged at fractional surface covering less than 50%; and, the rate is mass transport controlled, i.e. all adsorption and desorption processes depend on transport of bulk solute to and from the interface. As coverage exceeds 50%, surface ordering develops, and given sufficient contact time, adsorbed proteins undergo conformational and orientational changes to optimize interfacial interactions and system stability. Proteins less optimally adsorbed undergo desorption or exchange by larger proteins having more binding sites. The process rate becomes surface reaction limited (mass action controlled). With increasing residence time, protein adsorption becomes irreversible.
Several representative articles describing food soil deposition studies are: "Fouling of Heating Surfaces-Chemical Reaction Fouling Due to Milk", Sandu, C. and Lund, D., in Fouling and Cleaning in Food Processing (editors Lund, D., Plett, E., and Sandu, C.), pp. 122-167, University of Wisconsin-Madison Extension Duplicating, Madison, 1985; and, "Model Studies of Food Fouling", Gotham, S. M., Fryer, P. J., and Pritchard, A. M., in Fouling and Cleaning in Food Processing (editors Kessler, H. B. and Lund, D. B.), pp. 1-13, Druckerei Walch, Augsburg, 1989; and "Fouling of Milk Proteins and Salts-Reduction of Fouling by Technological Measures", Kessler, H. B., Ibid., pp. 37-45.
Theory suggests that irreversible protein adsorption begins as a tenacious monomolecular layer tightly bound by protein-surface interfacial forces. Polylayers and protein then deposit with repeated exposure, bound by protein--protein cohesive forces, each layer being progressively weaker in binding energy as the distance increases from the original substrate surface. Experimental observation and practical experience in milk process facilities confirm that several soil-clean cycles generally occur before protein films become visually discernable on surfaces, manifested by a light blue-brown to dark blue-black discoloration. Precise analytical confirmation can be made by a simple surface qualitative test utilizing Coomassie Brilliant Blue dye, which exists in two color forms--red and blue, the red rapidly converting to blue upon contact with protein. This dye-protein complex has a high extinction coefficient effecting great sensitivity in both qualitative and quantitative measurement of protein (see "The Use of Coomassie Brilliant Blue G250 Perchloric Acid Solution for Staining in Electrophoresis and Isoelectric Focusing on Polyacrylamide Gels"; Reisner, A. H., Nemes, P. and Bucholtz, C.; Analytical Biochemistry, Vol. 64, pp. 509-516 (1975); and, "A Rapid and Sensitive Method for the Quantitation of Microgram Quantities of Protein Utilizing the Principle of Protein-Dye Binding"; Bradford, M. M., Analytical Biochemistry, Vol. 72, pp. 248-254 (1976)).
As additional layers of protein deposit one upon another, a maximum thickness is likely reached above which cohesive protein--protein binding forces can be overcome by the mechanical, thermal, an detersive energies delivered to the soil by the cleaning program. This would explain results of elution experiments wherein surfaces previously soiled with milk and cleaned are then subjected to a second cleaning process having higher mechanical, thermal and detersive energies which can strip additional protein. However, practical observations suggest that protein films remain even at extremes of cleaning program conditions. A mechanism different than preferential displacement from absorptive sites is needed for protein film removal.
Researchers conducting soil removal experiments in the 1950's with the then new concept of recirculation cleaning (latter termed clean-in-place or CIP to encompass different methodologies) observed the occurrence of protein films on milk process equipment surfaces. Subsequently, the addition of hypochlorite to CIP alkaline detergent compounds was found to help remove protein film; and, this technology has been employed to-date by suppliers of cleaning compounds to the general food process industry. (For example, see "Effect of Added Hypochlorite on Detergent Activity of Alkaline Solutions in Recirculation Cleaning", MacGregor, D. R., Elliker, P. R., and Richardson, G. A., Jnl. of Milk & Food Technology, Vol. 17, pp. 136-138 (1954); "Further Studies on In-Place Cleaning", Kaufmann, O. W., Andrews, R. H., and Tracy, P. H., Journal of Dairy Science, Vol. 38, No. 4, 371-379 (1955); and, "Formation and Removal of an Iridescent Discoloration in Cleaned-In-Place Pipelines", Kaufmann, O. W. and Tracy, P. H., Ibid., Vol. 42, pp. 1883-1885 (1959).
Chlorine degrades protein by oxidative cleavage and hydrolysis of the peptide bond, which breaks apart large protein molecules into smaller peptide chains. The conformational structure of the protein disintegrates, dramatically lowering the binding energies, and effecting desorption from the surface, followed by solubilization or suspension into the cleaning solution.
The use of chlorinated detergent solutions in the food process industry is not without problems. Corrosion is a constant concern, as is degradation of polymeric gaskets, hoses, and appliances. Practice indicates that available chlorine concentrations must initially be at least 75, and preferably, 100 ppm for optimum protein film removal. At concentrations of available chlorine less than 50 ppm, protein soil build-up is enhanced by formation of insoluble, adhesive chloro-proteins (see "Cleanability of Milk-Filmed Stainless Steel by Chlorinated Detergent Solutions", Jensen, J. M., Journal of Dairy Science, Vol. 53, No. 2, pp. 248-251 (1970). Chlorine concentrations are not easy to maintain or analytically discern in detersive solutions. The dissipation of available chlorine by soil residues has been well established; and, chlorine can form unstable chloramino derivatives with proteins which titrate as available chlorine. The effectiveness of chlorine on protein soil removal diminishes as solution temperature and pH decrease--lower temperatures affecting reaction rate, and lower pH favoring chlorinated additional moieties.
These problems associated with the use and applications of chlorine release agents in the food process industry have been known and tolerated for decades. Chlorine has improved cleaning efficiency, and improved sanitation resulting in improved product quality. No safe and effective, lower cost alternative has been advanced by the detergent manufacturers.
However, a new issue may force change upon both the food process industry and the detergent manufacturers--the growing public concern over the health and environmental impacts of chlorine and organochlorines. Whatever the merits of the scientific evidence regarding carcinogenicity, there is little argument that organohalogen compounds are persistent and bioaccumulative; and that many of these compounds pose greater non-cancer health effects--endocrine, immune, and neurological problems--principally in the offspring of exposed humans and wildlife, at extremely low exposure levels. It is, therefore, prudent for the food process industry and their detergent suppliers to refocus on finding alternatives to the use of chlorine release agents in cleaning compositions.
A substantial need exists for a non-chlorine, protein film stripping agent for detergent compositions having applications in the food process industry, and having the versatility to remedy the problems heretofore described and presently unresolved.
Although enzymes were discovered in the early 1830's and their importance prompted intensive study by biochemists, public record of research into applications of enzymes in detergents first occurred in 1915 when German Patent No. 283,923 issued (May 4) to O. Rohm, founder of Rohm & Haas for application of pancreatic enzymes in laundry wash products. E. Jaag of the Swiss firm Gebrueder Schnyder developed this enzyme detergent concept further over the course of 30 years work; and, in 1959, introduced to market a laundry product, Bio 40, which contained a bacterial protease having considerable advantages over pancreatic trypsin. However, this bacterial protease was still not sufficiently stable at normal use pH of 9-10 and had marginal activity upon typical stains. It took several more years of research, until the mid 1960's, before bacterial alkaline proteases were commercial which had all of the necessary pH stability and soil reactivity characteristics for detergent applications.
Although use of enzymes in cleaning compositions did exist prior (see for example U.S. Pat. No. 1,882,279 to Frelinghuysen issued Oct. 11, 1932), large scale commercial enzyme containing laundry detergents first appeared in the United States in test market during 1966. Since that time, a large, but narrowly focused number of patents have been issued and reference articles published which disclose detergent compositions containing alkaline protease or enzyme class and subclass admixtures generally of proteases, carbohydrases and esterases. The vast majority of these patents target enzyme applications in consumer laundry pre-soak or wash cycle detergent compositions and consumer automatic dishwashing detergents. Close scrutiny of this patent library discloses the evolution of formula development in these product categories from simple powders containing alkaline protease (see for example U.S. Pat. No. 3,451,935 to Roald et al., issued Jun. 24, 1969) to more complex granular compositions containing multiple enzymes (see for example U.S. Pat. No. 3,519,570 to McCarty issued Jul. 7, 1970); to liquid compositions containing enzymes.
The progression from dry to liquid detergent compositions containing enzymes was a natural consequence of inherent problems with dry powder forms. Enzyme powders or granulates tended to segregate in these mechanical mixtures resulting in non-uniform, and hence undependable, product in use. Precautions had to be taken with packaging and in storage to protect the product from humidity which caused enzyme degradation. Dry powdered compositions are not as conveniently suited as liquids for rapid solubility or miscibility in cold and tepid waters nor functional as direct application products to soiled surfaces. For these reasons and for expanded applications, it became desirable to have liquid enzyme compositions.
Economic as well as processing considerations suggest the use of water in liquid enzyme compositions. However, there are also inherent problems in formulating enzymes into aqueous compositions. Enzymes generally denature or degrade in an aqueous medium resulting in the serious reduction or complete loss of enzyme activity. This instability results from at least two mechanisms. Enzymes have three-dimensional protein structure which can be physically or chemically changed by other solution ingredients, such as surfactants and builders, causing loss of catalytic effect. Alternately when protease is present in the composition, the protease will cause proteolytic digestion of the other enzymes if they are not proteases; or of itself via a process called autolysis.
Examples in the prior art have attempted to deal with these aqueous induced enzyme stability problems by minimizing water content (see U.S. Pat. No. 3,697,451 to Mausner et al. issued Oct. 10, 1972) or altogether eliminating water from the liquid enzyme containing composition (see U.S. Pat. No. 4,753,748 to Lailem et al. issued Jun. 28, 1988). As disclosed in Mausner et al. (Ibid.) and apparent from Lailem et al. (Ibid.), water is advantageous to dissolve the enzyme(s) and other water soluble ingredients, such as builders, and effectively carry or couple them into the non-aqueous liquid detergent vehicle to effect a homogenous, isotropic liquid which will not otherwise phase separate.
In order to market an aqueous enzyme composition, the enzyme must be stabilized so that it will retain its functional activity for prolonged periods of (shelf-life or storage) time. If a stabilized enzyme system is not employed, an excess of enzyme is generally required to compensate for expected loss. Enzymes are, however, expensive and are the most costly ingredients in a commercial detergent even though they are present in relatively minor amounts. Thus, it is no surprise that methods of stabilizing enzyme-containing, aqueous, liquid detergent compositions are extensively described in the patent literature. (See, Guilbert, U.S. Pat. No. 4,238,345).
Whereas the stabilizers used in liquid aqueous enzyme detergent compositions inhibit enzyme deactivation by chemical intervention, the literature also includes enzyme compositions which contain high percentages of water, but the water or the enzyme or both are immobilized; or otherwise physically separated to prevent hydrolytic interaction. For example of any aqueous enzyme encapsulate formed by extrusion, see U.S. Pat. No. 4,087,368 to Borrello issued May 2, 1978. For example of a gel-like aqueous based enzyme detergent, see U.S. Pat. No. 5,064,553 to Dixit et al. issued Nov. 12, 1991. For example of a dual component, two-package composition wherein the enzyme is separated from the alkalies, builders and sequestrants, see U.S. Pat. No. 4,243,543 to Guilbert et al. issued Jan. 6, 1981.
Enzyme containing detergent compositions presently have very limited commercial applications within the food process industries. A small, but significant application for enzymes with detergents is the cleaning of reverse osmosis and ultra filtration (RO/UF) membranes--porous molecular sieves not too dissimilar from synthetic laundry fabrics. Hard surface cleaning applications are almost non-existent with exception of high foam detergents containing enzymes being used occasionally in red meat processing plants for general environmental cleaning.
In 1985, a paper authored by D. R. Kane and N. E. Middlemiss entitled "Cleaning Chemicals-State of the Knowledge in 1985" (in Fouling and Cleaning in Food Processing; editors Lund, D. Plett, E., and Sandu, C.; pp. 312-335, University of Wisconsin-Madison Extension Duplicating, Madison, 1985) was delivered to the Second International Conference of Fouling and Cleaning in Food Processing. This paper emphasized CIP (clean-in-place) cleaning in the dairy industry. Within the text of this paper, the authors conclude that enzyme use in the food cleaning industry is not widespread for several reasons including enzyme instability at high pH and over time, enzyme and enzyme stabilizer cost, concern about residual enzyme and adverse effect on foodstuff quality, enzyme incompatibility with chlorine, slow enzyme reactivity necessitating long cleaning cycle times, and no commercial justification.
The present invention addresses and resolves these issues and problems.
The patent art does contain prior disclosure of enzyme containing detergent compositions having application on food process equipment. U.S. Pat. No. 4,169,817 to Weber issued Oct. 2, 1979 discloses a liquid cleaning composition containing detergent builders, surfactants, enzyme and stabilizing agent. The compositions claimed by Weber may be employed as a laundry detergent, a laundry pre-soak, or as a general purpose cleaner for dairy and cheese making processing equipment. The detergent solution of Weber generally has a pH in the range of 7.0 to 11.0.
The aforementioned prior teaching embodies high foam surfactants and fails to provide detergents which can be utilized in CIP cleaning systems.
U.S. Pat. No. 4,212,761 to Ciaccio issued Jul. 15, 1980 discloses a neat or use solution composition containing a ratio of sodium carbonate and sodium bicarbonate, a surfactant, an alkaline protease, and optionally sodium tripolyphosphate. The detergent solution of Ciaccio is used for cleaning dairy equipment including clean-in-place methods. The pH of the use solution in Ciaccio ranges from 8.5 to 11.
In Ciaccio, no working examples of detergent concentrate embodiments are disclosed. Ciaccio only asserts that the desirable detergent form would be as a premixed particulate. From the ingredient ranges discussed, it becomes obvious to one skilled in the art that such compositions would be too wet, sticky, and mull-like in practice to be readily commercialized.
U.S. Pat. Nos. 4,238,345 and 4,243,543 to Guilbert issued Jan. 6, 1981 teach a liquid two-part cleaning system for clean-in-place applications wherein one part is a concentrate which consists essentially of a proteolytic enzyme, enzyme stabilizers, surfactant and water; with the second concentrated part comprised of alkalies, builders, sequestrants and water. When both parts were blended at use dilution in Guilbert, the pH of this use solution was typically 11 or 12.
U.S. Pat. No. 5,064,561 to Rouillard issued Nov. 12, 1991 discloses a two-part cleaning system for use in clean-in-place facilities. Part one is a liquid concentrate consisting of a highly alkaline material (NaOH), defoamer, solubilizer or emulsifier, sequestrant and water. Part two is a liquid concentrate containing an enzyme which is a protease generally present as a liquid or as a slurry within a non-aqueous carrier which is ordinarily an alcohol, surfactant, polyol or mixture thereof. The use solution of Rouillard generally has a pH of about 9.5 to about 10.5.
Rouillard teaches the use of high alkaline materials; and, paradoxically, the optional use of buffers to stabilize the pH of the composition. Rouillard's invention discloses compositions wherein unstable aqueous mixtures of inorganic salts and organic defoamer are necessarily coupled by inclusion of a solubilizer or emulsifier to maintain an isotropic liquid concentrate. Rouillard further teaches that the defoamer may not always be required if a liquid (the assumption of term is "aqueous, stabilized") form of the enzyme is used in the second concentrate. This disclosure would seem to result from the use of Esperase 8.0 SL.TM. identified as a useful source of enzyme in the practice of the invention and utilized in working examples. Additional detail indicates Esperase 8.0 SL.TM. is a proteolytic enzyme suspended in Tergitol 15-S-9.TM., a high foam surfactant--hence the need for a defoamer and for a solubilizer or emulsifier. Rouillard still further discloses that proteolytic enzyme (Esperase 8.0 SL.TM.) of an by itself does not clean as effectively as a high alkaline, chlorinated detergent unless mixed with its cooperative alkaline concentrate.